Probes mounted on the wall of the fuselage or the engine air intake of an aircraft to measure air temperature are known in the art. Such probes are designed to operate in environments and at altitudes where the temperatures are much lower than 0.degree. C. and in atmospheres that may be charged with supercooled water molecules.
A constraint inherent to the operation of such probes is that they must include means to prevent the formation and accumulation of ice in the proximity of the sensitive element of the probe. Indeed, such an ice accumulation would falsify the measurements effected by the probe.
A prior art solution to the problem of preventing the accumulation of ice consists in heating parts of the probe in the proximity of the sensitive element and in correcting the systematic measurement error due to such heating
Such a solution is generally acceptable for measuring the temperature in environments containing relatively little supercooled water (for example less than 1.25 g of supercooled water per m.sup.3 of air), but is not suitable in itself for de-icing the probe correctly in atmospheres with a higher moisture content.
This is because, in this case, the only way to guarantee that the ice will melt is more intensive heating, but melting the ice causes a flow of water droplets which come into contact with the sensitive element as they flow over it and thereby falsify the measurements effected by the probe.
Also, more intense heating is not an economically viable solution because of the non-negligible increased electrical power consumption and the associated cost.
Another way to de-ice the probe, used in conjunction with heating, is to define the geometry of the probe to maximize deflection of the trajectories of supercooled water particles contained in the flow of air around the probe so that a high proportion of the particles are kept away from the sensitive element of the probe.
Thus probes exist in which the sensitive element is accommodated in an internal passage which only some of the water particles enter when the air flows around the probe. However, that solution has the drawback of complicating manufacture of the probe, as it is then necessary to provide complex arrangements for connecting electrical cables to supply power to the sensitive element and collect the signals it delivers.
Moreover, in that case, the sensitive element S in a passage into which only part of the air flow enters, and is therefore ventilated only slightly by the airflow, which means that it must be of high sensitivity, which generally increases its cost and makes it more fragile (through the use of ceramic temperature-measuring components, for example).
Another prior art probe has an airfoil profile with the sensitive element in a duct passing obliquely through the thickness of the profile. The sensitive element in that probe is located in a flow that is secondary to the main flow of air around the probe, said secondary flow conveying significantly fewer water particles than the main flow. With only moderate heating of the probe, it is possible to measure reliably the temperature of environments with a relatively high moisture content and at relatively low temperatures.